Abstract:

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Atomistic simulations using molecular dynamics (MD) method are conducted to check the
conditions of the onset of fracture at the interface edges with a variety of angles. The simulations are
facilitated with model bi-material systems interacting with Morse pair potentials. Three simulation
models are considered, i.e. the interface edges with angles 45°, 90° and 135°, respectively. The
simulation results show that, at the instant of crack initiation, the maximum stresses along the
interfaces reach the ideal strength of the interface; also, the interface energies just decrease to below
the value of the intrinsic cohesive energy of the interface. And the onset of fracture at the interface
edges with different geometries is controlled by the maximum stresses or the cohesive interfacial
energy.

Abstract: Cross-sectional nanoindentation (CSN) is a new method for measuring interface adhesion
of thin films. The interfacial energy release rate (G), characterizing interfacial adhesion, is
calculated from the material and geometrical parameters relevant to the test. Effects of residual
stresses on G and crack tip phase angle Ψ, have been studied by finite element simulation in this
study. The results show tensile residual stresses increase G and compressive stresses reduce it, and
they have similar effects on the magnitude of Ψ.

Abstract: In order to solve the problem of diamond film crack when deposited on molybdenum substrate to improve the preparation quality of diamond film and the rate of finished products , the distributions of thermal residual stress components in diamond film and at interface between the film and molybdenum substrate were simulated by finite element method in the case of whether to consider the plastic deformation of molybdenum substrate or not, moreover, the influence of thermal residual stress upon the failure of film was analyzed. Results show that thermal residual stress is more coincidental with experimental data when the plastic deformation of molybdenum substrate is considered. There are large tensile radial stress and tensile axial stress in the vicinity of upper surface of the film, which is the primary cause for the film to crack.

Abstract: Interfacial potential of Fe [110]/TMC[001] (TM=V, Nb and Ta) are obtained with adhesive energy and the inversion method. The interfacial stability and tensile fracture properties of the semi-coherent interfaces of the Fe [110]/TMC[001] (TM=V, Nb and Ta) are studied based on the interfacial potentials. Results indicated that Fe/VC interface is more stable than the Fe/TMC (TM=Nb and Ta) interfaces.

Abstract: A procedure based on the Linear Elastic Brittle Interface Model (LEBIM) combined with the Coupled Criterion of Finite Fracture Mechanics (CCFFM) is successfully implemented in a 2D Boundary Element Method (BEM) code. In the original LEBIM formulation, the values of the interface strength, fracture toughness and stiffness are dependent on each other. Therefore, for a large interface stiffness, when the elastic interface tends to a perfect (infinitely stiff) interface, LEBIM is not able to properly characterize the crack propagation. The use of the CCFFM applied to LEBIM, with both the stress and energy criteria imposed as independent fracture conditions, allows to uncouple the interface fracture toughness and strength, obtaining realistic predictions for crack propagation even for stiff interfaces. This code is successfully applied to the problem of debond onset and growth in the pull push test. A benchmark problem is solved, focusing on the convergence of the load-displacement curve and crack-tip solution for h-refinements of BE meshes.